IBM BSC CRC?

[Ethan Dicks]

On Sun, Jan 26, 2020 at 2:59 PM Mattis Lind via cctalk
<cctalk at classiccmp.org> wrote:
> Hello IBM BSC Experts!

I used to be one 25 years ago, but it's been that long since I've even
set up a BSC line.

> I am trying to figure out the CRC algorithm used by IBM BSC...
>
> From this document (
> http://bitsavers.trailing-edge.com/pdf/ibm/datacomm/GA27-3004-2_General_Information_Binary_Synchronous_Communications_Oct70.pdf
> )
> I get that the CRC calculation is reset on SOH (01h) or STX (02h) and
> accumulates until and including the ETX (03h). (excluding any SYN (32h)
> characters).

That's a good document.

What we used as our "gold standard" in the 80s was a "Data 100" manual
for a 3rd party BSC workstation.  The documentation went way beyond
CRC-16 and message formats.  It delved deeply into the whole protocol.
I don't remember the vendor, and I know I don't have a scan of it.  I
was not able to quickly find a copy online but I admit I didn't search
more than a few minutes.  It would be a good resource to locate.

-ethan